Electric arc furnace



March 19 1946.

H. 1 KUEHLTHAU E-r AL ELECTRIC ARC URNACE Filed May 17, 1944 5 Sheets-Sheet 1 jez/62224515.

March 19, 1946 H. l.. KUEHLTHAU ET As. 2,396,663

ELEQTRI C ARC FURNACE Filed May 17, 1944 5 Sheets-Sheet 2 March 19,v.1946. H.- L. KUEHLTHAU ET AL 2,395,663

ELECTRIC ARG FURNACE Filed May 17, 1944 5 Sheets-Shea?l 5 March'19, 1946- H. 1 KUEHLTHAU ET AL 2,396,663v

ELECTRIC ARC- FURNAGE Filed May 17. 1944 5 Sheets-Sneet 4 March 19, 1946. H, L. KUEHLTHAU ET AL 2,395,553

` ELECTRIC ARC FURNACE Filed May 17, 1944 5 Sheets-Sheet 5 f 'wu Patented Mar. 19, 1946 ELECTRIC ARC FURNACE Hugo L. Kuehlthau, Chicago, Charles W. Vokac, Cicero, and Michael Del Monte, La Grange, Ill., assignors to Whiting Corporation, Harvey, Ill., a corporation of Illinois 20 Claims.

The present invention relates generally to electric arc furnaces for use in metallurgy. More particularly the invention relates to that type of electric arc furnace which is known in the art as a top charge furnace and as its main or principal component parts comprises: (1) an open top shell which is adapted to be charged through the top thereof with metallic material to be processed or reduced to molten form, has a lining of refractory material and in addition a side spout for discharging the molten metal, and is mounted so that it is tiltable back and forth between a normal upstanding position and an inclined pouring position wherein the side spout extends downwards; (2) `a refractory lined roof which normally rests on the top portion of the liningr of the shell where it serves as a closure for the shell in connection with a metal melting operation and is pivotally supported so that it may be swung laterally to one side of the shell into an open position wherein the top of the shell is exposed for charging purposes; (3) a plurality of upstanding electrodes which extend slidably through holes in the central portion of the roof and are provided with means for supplying them with electric current; and (4) a plurality of electrode supporting members which are associated respectively with, and correspond in number to, the electrodes and consist of horizontally extending cantilever type arms having clamps at their outer ends for the upper ends of the electrodes, and vertical extensions which are connected to the inner ends of, and depend from, the arms and are slidably mounted so that the members may be shifted in order to effect raising and lowering of the electrodes with respect to the shell.

In an electric arc furnace of this type it has heretofore been proposed to utilize as a mount for the roof a laterally extending bracket on the roof and a shaft which depends from the bracket, fits slidably and rotatably in a tubular member on the side wall of the shell and permits the roof to be raised preparatory to being swung laterally into its open position and also to be lowered onto the upper portion of the lining of the shell after it has been swung back into overlying relation' with the shell. It has also been proposed to mount the electrode supporting members on the bracket of the mount for the roof in order that they, together with the electrodes, tilt with the roof and-shell-in connection with a molten metal pouring or discharging operation and also swing laterally to one side of the shell when the roof is swung into its open position wherein the Application May 17,1944, serial No. 535,930

top of the shell is exposed for charging purposes. In practice it has been found that an electric arc furnace wherein the roof has a mount of the aforementioned character and the electrode supporting members are mounted on the bracket of the mount, is subject to certain objections. In the rst place when the roof is in its operative position wherein it rests on the top portion of the refractory lining of the shell the shell lining is subjected to not only the weight of the roof but also the weight of the electrodes, the electrode supporting members, the laterally extending bracket, and the shaft and hence has but a short life and must be replaced at frequent intervals. Secondly, when the roof is in its operative or closed position the refractory shell lining ls subjected to unequal downward pressure due to the fact that the electrode supporting members are connected to the bracket of the mountwhich is laterally offset with respect to the axis or center of the shell.

The primary object of the invention is to provide an electric arc furnace which is an improvement upon, and eliminates the disadvantages or defections of, previously designed furnaces of the same general type and is characterized by the fact that it includes a bracket structure which is pivotally connected to the shell so that it is only capable of swinging laterally, serves to support the electrode supporting members, and has means whereby the roof is suspended so that it may be independently raised preparatory to being swung laterally into its open position and also independently lowered onto the top portion of the shell lining after it is swung back into overlying relation with the shell following a shell charging operation. By providing the bracket structure and utilizing the roof suspension means the refractory lining of the shell is subjected to only the weight of the roofl when the roof is in its operative or closed position and the downward pressure which is exerted on the shell lining by the roof is uniform or equal and hence the life of the shell lining is materially increased and it is resultantly not necessary to replace the shell lining at frequent intervals.

Another object of the invention is to provide an electric arc furnace of the last mentioned type and character in which the suspension means for raising and lowering the roof Withrespect to the shell is of simple and novel design, and the bracket structure embodies novel mounting means for the electrode supporting members and has simple power means whereby it may be swung laterally away from the shell in connection also swung laterally toward the-shell in connection with return movement of the root' into overlying relation with the shell.

A further object of the invention is to provide an electric arc furnace which is generally of new and improved construction, effectively and emciently fulfills its intended purpose and is characterized by simplicity of design and long life.

Other objects of the invention and the various advantages and characteristics of the present electric arc furnace will be apparent from a consideration of the following detailed description.

The invention consists in the several novel fea# tures which are hereinafter set forth and are more particularly defined by claims at the conclusion hereof.

In the drawlngswhich accompany and form a part of this specication or disclosure and in which like numerals of reference denote corresponding parts throughout the several views:

Figure 1 is a side view of an electric arc furnace embodying the invention, illustrating in detail the construction, design and arrangement of the bracket structure which is pivotally connected to the shell for lateral swinging movement, serves to support the electrode supporting members and has associated therewith roof suspension means whereby the roof may be raised and lowered relatively thereto out of and into its closed position with respect to the shell;

Figure 2 is a side view of the furnace taken at right angles to Figure l. and showing the manner in which the receptacle is mounted so that it is tiltable back and forth between a normal upstanding position and an inclined pouring position wherein the side spout extends downwards;

Figure 3 is a plan view of the furnace illustrating the manner in which the bracket .structure is capable of being swung laterally away from the shell in order to shift'the roof into its open position and also laterally toward the shellin order to bring the roof into overlying relation with the shell after a shell charging operation;

Figure fi is a vertical section taken on the line 4 4 of Figure 2 and showing in detail the manner in which the vertical extensions of the electrode supporting members are slidably mounted with respect to the bracket structure;

Figure 5 is a fragmentary side View oi the furnace with certain parts thereof broken away and other parts thereof shown in section in order to illustrate in detail the suspension means for eifecting raising and lowering of the roof relatively7 to the bracket structure and the shell;

Fig. 5a is an enlarged section of one of the re'- movable connections between the roof suspenf sionv means and the roof; and

Figure 6 is an enlarged horizontal section on the line 6--6 of Figure 2.

The electric arc furnace which is shown in the drawings constitutes the preferred form or embodiment of the invention. It is of the so-called top charge variety and serves as a medium or instrumentality for processing or reducingto molten form metallic material. As its main or principal parts the furnace comprises a shell I0, a roof Ii, a bracket structure I2, suspension means I3 for raising and lowering the roof relatively to the bracket structure, a plurality oi upstan'ding electrodes It, and a plurality of electrode supporting members l5.

Shell The shell in has an open top whereby it may @Saddles with shift of roof into its open position and be charged with the metallic material to be processed or reduced to molten form, and comprises a cylindrical side wall le and a downwardly dished or bulged bottom il. it also comprises a lining ill of refractory material and has a discharge spout I9 and a slag door 2li. The side and bottom walls are formed of heavy plate metal and are welded or otherwise xedly secured together. The upper margin of the side wall I5 is reenforced by an angle bar type ring 2l. The spout I9 and the slag door 20 are mounted on the side wall it of the shell and are preferably positioned one diametrically opposite the other. As shown in Figure 4, the refractory lining I8 covers the inner surfaces of the side and bottom walls of the shell and is cup shaped. The upper or top portion of the refractory lining I8 projects a slight distance above the reenforcing ring 2i around the upper margin of the shell side wall IB. The shell is mounted by Way ofa pair of gear segments 22 and a pair of racks 23 so that it may be tilted back and forth between a normal upstanding position and an inclined pouring position wherein the spout I9 extends or projects downwards. The gear segments 22 are disposed in laterally spaced, parallel relation and underlie and are welded or otherwise flxedly secured to the bottom wall Il of the shell I0. They rest upon, and mesh with, the racks 23. The latter are mounted on the foundation over which the furnace is disposed. When the shell it is urged in the direction of the spout I 9 it tilts7 as shown by dotted lines in Figure 2, into a position wherein the spout i9 extends downwards and serves to discharge the molten metal in the shell. When the shell is urged in the reverse direction it tilts upward into its normal opstanding position. The shell is tilted or rocked back and forth between its pouring and normal positions by conventional or standard power actuated mechanism (not shown). It is contemplated that the shell will be charged while in its normal upstanding posin tion and will be retained in such position until the charge is reduced to molten form by the heat which is generated as the result of the supply of current to the electrodes lli. After the charge is melted or processed to the desired extent the shell is tilted so as to eifect discharge of the molten metal via the spout le.

The roof Il is mounted, as hereinafter described, so as to swing laterally baclt and forth between a normal or operative position wherein it overles and seals thev shell and an open or inoperative position wherein it is disposed at one side of the shell and exposes the top of the shell for charging purposes. It is substantially the same in diameter as the side wall Iii of the shell and comprises an upwardly bulged circular or disc-like lining 25 of refractory material, and a metallic annulus 26. As shown in Figure Ll, the annulus 26 is channel shaped in cross section and has the flanges thereof extending inwards. The margin of the refractory lining 25 rests upon the lower flange of the annulus 26. The lining 25 is of substantial thickness and when the roof is in its closed or operative position, forms with the lining I8 of the shell IU a substantially closed or sealed chamber 21 for the charge of metallic material to be reduced to molten form. The margin of the lining 25 of the roof Il is adapted to rest on the top or projecting portion of the lining I8 of the shell I0. It is contemplated during use of the furnace that in connection with a shell charging operation the roof II will first be raised to a slight extent so as to disengage the lining 25 from the lining I8. Thereafter the roof will be swung laterally to one side of the shell so as to expose the open top of the shell for introduction of the charge of material. After the material is introduced into the shell the roof II is swung back into overlying relation with the shell and is then lowered so as to bring the at bottom surface of the marginal portion of the roof lining 25 into abutment or seated relation with the toiJ of the shell lining I8.

Bracket structure The bracket structure I2 carries the roof suspension means I3 and lthe electrode supporting members I5 and is hinged or pivotally connected to theshell so that it is capable of being swung laterally away from the shell in order to shift the roof into its open position and also laterally toward the shell in order to bring the roof into overlying relation with the shell after a shell charging operation. It comprises an arm 28, a plate 29 and a U-shaped frame 30. The arm 28 is preferably formed of cast metal and extends horizontally when the shell I is in its normal upstanding position wherein the axis thereof is truly vertical. It is vertically and horizontally elongated and embodies at one end thereof an integral upstanding tubular part 3I. A rectangular plate 32 extends across, and is welded or otherwise xedly secured to, the upper end of the tubular part 3| and forms a closure cap for said part. In addition to the tubular part 3| the arm embodies an outwardly extending top flange 33, an outwardly extending bottom flange 34, and an outwardly extending end flange 35. Such flanges are formed integrally with the arm and serve, together with a pair of upstanding webs 36, to stiffen or reenforce the arm as 'a whole. The end flange 35 is located at the distal end of the arm 28 and has its ends joined to the adjacent ends of the top and bottom flanges 33 and 34. The webs 36 are formed integrally with the outer surface portion of the arm 28 and have the upper ends thereof joined to the central portion of the top flange 33 and their lower ends joined to the central portion of the bottom flange 34. As Ashown in Figures 1 and 2, the tubular part 3l of the arm 28 surrounds and is mounted rotatably on the upper end of an upstanding shaft 31. The lower end of such shaft is carried by a vertically ex- `tending bracket 38 on the side wall I8 of the shell I0. The bracket 33 is preferably in the form of a metallic casting and projects laterally from the side wall of the shell. It embodies at its inner portion an upstanding arcuate wall 39 which, as shown in Figure 6, is curved conformably to the shell side wall i and is welded or otherwise xedly secured in place. The outer portion of the bracket 38 is provided with integral semicircular parts 4G and these are spaced vertically apart and extend normally horizontally and have outwardly extending integral lugs 4I at their ends. The lower end of the shaft 31 is seated in the semicircular parts 40 and is clamped in place by way of a pair of semicircular clamping members 42. The latter are associated, respectively with, and are arranged in opposed relation with respect to, the semicircular parts 4U of the bracket 38 and have outwardly extending end lugs 43. Bolts 44 extend through the lugs 4I and 43 and serve to clamp the members 42 and thus lock or fix the lower end of the shaft 31 to the bracket 38. The bracket 38 is so arranged that it operates to space the shaft 31 asllght distance from the shell I0 and also to hold the shaft so that the axis thereof is in true parallel relation with the axis of the shell. A pin 45 extends through the tubular part 3I of the arm 28 and into an annular groove 46 in the upper end of the shaft 31 and serves to hold the tubular part against axial displacement with respect to the shaft while at the same time permitting the arm to swing laterally to and from the furnace shell I 0.

The plate 29 of the bracket structure I2 extends vertically and is rectangular so far as shape or contour is concerned.V It is disposed inwards of the inner face of the arm 28 and is arranged in parallel relation with the arm. Pairs of upstanding cross plates 41 extend between the arm 28 and the plate 29 and serve to hold the latter in rigid Vconnected relation. As shown in Figure 6, the

cross plates of each pair are spaced laterally apart to denne between them an upstanding slideway 48. The outer end edges of the cross plates 41 abut against, and are welded to, the inner face of the arm 28 and the inner end edges of said cross plates abut against, and are welded to, the outer face of the plate 29. The upper margin of the plate 29 is reenforced by a longitudinally extending I-beam 49 and this is disposed inwards of the plate and has the inner edges ofits top and bottom flanges welded to the upper portion of the inner face of the plate 29. As shown in Figure l, the I-beam 49 is positioned so that the top flange thereof is flush with the upper edge of said plate 29. A pair of normally horizontal plates 50 overlie, and are welded to, the ends of the top flange of the I-beam 49 (see Figure 3).

The U-shaped frame 30 of the bracket structure I2 projects inwards from the arm 28 and the plate 29 and overlies, and is spaced above, the roof I I. It extends horizontally when the shell I0 is in its normal or upstanding position and consists of a pair of parallel laterally spaced side legs 5I and a cross leg 52. 'I'hese three legs are formed of tubular metal stock of rectangular cross section in order that the frame 30 as a whole is hollow and hence may have water or any other coolant circulated therethrough for cooling purposes. The ends of the cross leg 52 of the frame 30 are suitably connected to the ends of the side legs that are farther from the arm 28. The other ends of the sidelegs, i. e., the ends that are nearer the arm 28, rest on, and are welded to, the plates 58 at the ends of the I-beam 49. The inner end of one of the side legs 5I of the frame 38 is closed by a plate 53 having a nipple 54 for attachment toa iiexible water supply tube 55. The inner end of the other side leg of the frame is closed by a plate 56 having a nipple 51 for attachment to a flexible water discharge tube 58. The legs of the frame 30 are so arranged that the water which is introduced via the nipple 54 circulates first through said one side leg, then through the cross leg 52 and then through the other side leg to the nipple 51.

The bracket structure l2 is swung laterally away from and towards the shell Ill for roof positioning purposes by means of power means comprising a piston-cylinder device 59. The latter, as best shown in Figure 6, is positioned adjacent the upper end of the shaft carrying or supporting bracket 38 and consists of a cylinder 38 and a piston 6I. The cylinder 60 extends horizontally when the shell I0 is in its normal upstanding position and has an end wall 62 at one end thereof and an end wall 63 at its other end. The end wall B2 of the cylinder is provided with an externally disposed U-shaped lug t@ which straddles a hori-I zontally extending lug 65 and is pivotahy connected thereto by way of a pin dit. The lug dit, as shown in Figure 6, is welded to the upstanding arcuate wall 39 at the inner portion of the bracket Sii. The pivot pin t@ permits the piston-cylinder devicev 59 to swing laterally. The piston iii is lslidably mounted in the cylinder t@ and is provided with a piston rod l which extends through, and is slidably mounted in, a stumng box ttl on the end wall 63 of the cylinder. The inner end of the piston rod is nxedly connected to the piston and the outer end of the rod is provided with a U-shaped lug 59 which straddles a laterally extending normally horizontal lug l@ on the lower end of the tubular'part 3i of the arm 28 and is pivotally connected to said lug l@ by a normally vertically extending pin l l. The lug li! is welded or otherwise xedly secured to the lower end of the tubular part 3l and is so arranged with respect to the lug 65 that the piston-cylinder device 59 is not in dead center relation with the shaft 3l. The cylinder 60 is provided at its ends with nipples 'l2 and 13 whereby uid under pressure may be introduced into it. The nipple 'l2 is disposed adjacent the end wall 62 and the nipple "it, as shown in Figure 6, is disposed adjacent the end wall (53. When fluid under pressure is introduced into the cylinder via the nipple 'l2 while the nipple i3 is vented the piston ti is forced towards the cylinder end wall t3 and operates through the medium of the piston rod di and the laterally extending lug 'l0 on the tubular part 3i of the arm 2t, to swing the bracket structure l2 laterally away from the shell it. When fluid under pressure is introduced into the cylinder via the nipple lt while the nipple 'l2 is vented or open to atmosphere the piston 6| is forced toward the cylinder end wall 62 and operates through the medium of the piston rod 67, the lug 'id and the tubular part 3 i, to swing the bracket structure laterally toward the furnace shell Il). The stroke of the piston ti is such that when the piston is in abutment with the cylinder end wall b2 the bracket structure is disposed wholly out of overlying relation with the shell, as shown by dotted lines in Figure 3, and. when the piston is in abutment with the cylinder end wall t2 the frame Sii of the bracket structure is in direct overlying relationwith the shell, as shown by full lines in Figure 3. The piston-cyl-l inder device 59 constitutes simple means for swinging the bracket structure i2 to and from the shell il) in connection with shift of the roof il into and out of its normal or operative position. T n a small sized furnace a hand lever or other manually operated means (not shown) may be substituted for the piston-cylinder device 59.

Roof suspension means The-roof suspension means it serves as a medium for supporting the roof so that it is capable of being raised and lowered relatively to the bracket structure l2. It is mounted on .the bracket structure and comprises a plurality of flexible elements in the form of chains 14. The latter are shown in the drawings as being four in number and-are associated respectively with,

the upper ends of the pipe sections '16. The lower relation or alignment with the holes 76C.

` assenso ends or the pipe sections liti are removably connected to the metallic annulus 2e or the roof il by way of upstanding stub shafts lo? and wedge shaped keys lob (ses Figure 5e) The upper ends oi the stub shafts nt snugly within, and are welded to, the lower ends of the pipe sections i6. The lower ends of said stub shafts are of reduced diameter, extend through holes loc in the top flange or the annulus 265 and nt removably in sleeves ltd. Ilihe latter are disposed beneath, and have lthe upper ends thereof welded to, the top nange of the annulus 26 and are in registering The wedge shaped keys 'lob extend through slots 15 in the web of the annulus 2t and have the inner ends thereof disposed iti-aligned slots in the sleeves 'ld and the lower ends of the stub shafts 16u. When the keys itl are driven inwards into their normal or operative position they wedge the stub shafts 16a downwards so that the enlarged upper ends thereof are clamped against the upper surface ci :the top nange of the annulus 26, By reason of the fact that the lower ends of the pipe sections i6 are removably connected to the annulus of the roof the roof may be released from the suspension means when it is desired to replace it. In connection with replacement of the roof it is only necessary to withdraw the wedge shaped keys ich and then swing the bracket structure i2 away from the shell l0. Upon shirt or the bracket structure away from the shell the root is exposed and hence may be removed by an overhead crane or the like and a new roof substituted for it. The central portions of the chains le extend through upstanding pipe sections il adjacent the ends of the side arms 5l of the frame 3b. As shown in Figure 5, the pipe sections ll are of greater diameter than the pipe sections and have the lower ends thereof in loose telescopic relation with said pipe sections it. By reason of the fact that the lower ends o1 the pipe sections lill are in telescopic relation with. the pipe sections le the roof l i is permitted to move vertically to and from the frame 363 of the bracket structure while at the same time it is held against lateral displacement relatively to the frame. The upper ends of the pipe sections il extend through, and are welded to, the ends of the side legs 5l of the irl-shaped frame til. The upper ends of the chains ld are trained around sector shaped sheaves lit and are an-n chored to the upper portions of the latter by way oi? eye-bolts lb. The sheaves are mounted on stub axles which are carried respectively by pairs of triangular'bracket plates 3i. The bracket plates, as shown in Figure 5, are welded to, and project upwards from, the side portions of the side legs til of the U-shaped frame 3i). The upper portions of the bracket plates are provided with holes in which the ends of the stub axles b are mounted. The eyes of the eye-bolts is are connected to the upper end links of the chains 'lf3 and the shanks of the bolts extend through apertured cross webs B2 on the upper portions of the sheaves and have nuts 83. The latter abut against the aperture defining portions of the cross webs 32 and constitute means Whereby the chains 'It may be adjusted with respect to the sheaves. When the nuts 83 are tightened the chains are drawn upwards with respect to the sheaves and when the nuts are loosened the chains are downwardly paid out relatively to the sheaves. By properly adjusting the nuts the chains 7M may be so positioned with respect to the sheaves that they hold the roof l I in a truly horizontal position when it is raised prior to being swung laterally into its open position. When the sheaves 18 are rotated in a clockwise direction as viewed in Figure 5, i. e., so thatthey wind up the chains 14, the roof is raised. When lthe sheaves are reversely rotated the chains are paid out and result in lowering of the roof relatively to the U-shaped frame 30 of the bracket structure |2.

The sheaves 18 are coniointly turned for roof raising or lowering purposes by power mechanism which constitutes part of the suspension means I3 for the roof Il and comprises an upstanding cylinder-piston device 84, an arm 85, a normally horizontal rock shaft 8B, a pair of arms 81, a pair of links 88, a pair of bell cranks 89 and a pair of links 90. The upstanding cylinder-piston device 84 consists of a cylinder 9| and a piston 92 and is located directly outwards of the arm y28 l is formed integrally with, the central portion of the bottom flange 34 of the arm 28. The pin 91 extends through registering holes in the lugs 95 and 99 and permits the cylinder-piston device 84 to swing to and from the arm 28. The piston 92 is slidably mounted in the cylinder` 9i and is provided with a piston rod 98 which extends through and is slidably mounted in a stufng box on the end wall 94 of the cylinder 9|- The inner or lower end of the piston rod is xedly connected to the piston 92 and the outer or upper end of the rod is provided with a U-shaped lug 99. The cylinder 9| ofthe cylinder-piston device 84 is adapted to receive lluid under pressure for piston operating purposes by way of nipples and 10| at its ends. The nipple |00 is located immediately adjacent the end wall 93 and the nipple 0| is located directly beneath the end wall 94. When fluid under pressure is introduced into the cylinder via the nipple |00 whileV the nipple 10| is vented the piston 92 is forced upwards towards the cylinder end wall 90. When fluid under pressure is introduced into the upper end of the cylindervia the nipple i0! while the nipple |00 is vented the piston 92 is forced downwards towards the cylinderV end wall 93. The U-shaped lug 99 at the upper end of the piston rod 98 surrounds one end of the arm 85 and is pivotally connected thereto by a pivot pin |02. The other end of the arm 85 is xedly connected to the central portion of the rock shaft 8S. As shown in Figure 2 the rock shaft is located directly outwards of the upper portion of the arm 28 and has its ends journalled in bearings |03 on the upper corner .portions of the arm 28. When the piston 92 is forced upwards as heretofore pointed out, the arm 85 operates to turn the rock shaft 86 in a counterclockwise direction as viewed in Figure ll and when the piston 92 is forced downwards the arm 85 operates to turn or rock the shaft 86 in a clockwise direction as viewed in Figure 1. In a small sized furnace a hand lever or other suitable manually actuated means (not shown) may be used to rock the shaft 86 for roof raising and lowering purposes instead of the pistoncylinder device 14. The arms 81'are xedly connected to, and project outwardly from, the ends of the rock shaft 86 as shown in Figure 2, The links 88 are disposed in an upstanding position and are aligned with the side legs 5| of the U-shaped frame 30. The lower ends of the links 88 are pivotally connected to the outer or distal ends 0f the arms 81, The bell cranks 89 comprise outwardly extending arms |04 and upwardly extending arms |05 and have the central portions thereof connected by pins |06 to brackets |01 on the upper corners of the arm. 28 of the bracket structure l2. The pins |06 are so arranged that the bell cranks 89 are permitted to Vswing in vertical planes when the shell i0 is in its normal upstanding position, The upper ends of the links 89 are pivotally connected to the outer or distal ends of the upwardly extending arms |04 of the bell cranks 89. The links 90 are disposed above and in parallel relation with the side legs 5| of the U-shaped frame 80. The ends of the links 99 that are disposed adjacent the arm 28 are pivotally connected to the outer or distal ends of the arms l05 of the bell cranks 89. The portions of the links 90 that are adjacent the sector shaped sheaves 19 are pivotally connected by pins I 08 to upstanding lugs |09 on the upper portions of the sheaves. When the piston 92 of the piston-cylinder device -84 is forced downwards by introducing fluid under pressure into the upper end of the cylinder 9| via the nipple iti the rock shaft 98 is caused to rock in a clockwise direction as viewed in Figure 1 and operates through the medium of the arms 81 and the links 89 to rock or swing the bell cranks 89 in a clockwise direction as viewed in Figure l. Such-swinging of the bell cranks operates through the medium of the links 90 to turn the sheaves 18 in a clockwise direction shifted laterally into its open position by swinging the bracket structure |2 through the medium of the piston-cylinder device 59. As heretofore pointed out, the roof when in its open or inoperative position exposes the shell so that it may be charged with a batch of metallic material to be processed or reduced to molten form. After charging of the shell the roof is returned to overlying relation with the shell by reverse swinging of the bracket structure i2 through the medium of the cylinder-piston device 59, After the roof is shifted into overlying relation with the shell it is lowered into its closed or operative position by introducing fluid under pressure into the lower end of the cylinder 9| via the nipple |00 and venting the nipple lili. As soon as fluid under pressure is introduced into the lower end of the cylinder 9| the piston 92 is forced upwardsand, as previously pointed out, operates through the medium of the arm to rock the rock shaft 89 in a counterclockwise direction as viewed in Figure l. Such rocking on the part of the rock shaft operates through the medium of the arms 91 and s the links 88 to rock the bell cranks 89 in a counterclockwise direction and such rocking on the part of the bell cranks operates through the medium of the links 99 to turn the sheaves 18 in a counterclockwise direction as viewed in Figures l and 5 and resultantly to pay out the chains 14 and effect lowering of the roof. When the roof is in its closed position its weight alone is imposed on therefractory liningl 21 of the shell l0 and hence the lining 21 is subjected to a minimum amount of downward pressure and its life is thereby materially increased. By providing the roof suspension means |3 the weight of the bracket structure I2, the electrodes and the elec- ,lis uniform or equal.

trode supporting members is not imposed upon the lining of the shell when the shell is in its closed or operative position. Another advantage f of utilizing the specic roof suspension means I3 resides in the fact that the downward pressure which is exerted by the roof on the shell lining In other words, when the roof is in its closed position the top portion of the shell lining 2l is subjected to uniform downward pressure with the result that the side portion of the lining deteriorates uniformly and it is not necessary to replace the shell lining at frequent intervals.

Electrodes The electrodes I are arranged in an upstanding position and extend slidably through holes IIIl in the central portion of the refractory lined roof II. They are supplied with electric current and serve, when the furnace is in operation, to produce electric arcs, the heat of which omrates to reduce to molten form the charge of metallic material in the chamber 2l. In the drawings three electrodes are illustrated. It is to be understood, however, that a lesser or greater number of Velectrodes may be employed, depending upon the size orlcapacity of the furnace. Normally the electrodes are positioned so that the lower ends thereof project into the chamber 2l; When it is desired to charge the shell Ill the electrodes are raised so that the lower ends thereof are positioned above the top portion of the lining I8of the shell. When the electrodes are raised to such an extent the roof `Il may be swung laterally into its open position by swinging the bracket structure I2 away from the shell as heretofore described.

Electrode supporting members The electrode supporting members I are associated respectively with, and correspond in number to, the electrodes I4 and consist of normally horizontal cantilever type arms III and normally vertical extensions II2. The outer ends of the arms III are provided with clamping devices II3, which surround the upper ends of the Y electrodes I4 and serve releasably to connect the electrodes to the arms. The inner ends of the arms III, i. e., the ends that are remote from the clamoiner devices II3, overlie, and are bolted to, platesII4 on the upper ends of the vertical extensions II2 of the electrode supporting members I5. Said extensions II2 are hollow and have open lower ends. They extend through, and are slidably mounted in, the slideways 48 between the cross plates 41 so that the supporting members I5 are capable of being shifted in order to eiect lowering and raising of the electrodes with respect to the shell II). As shown in Figure 6. the cross plates 4l are provided with rollers II5 which are disposed in the slid-aways 48, engage the end walls of the vertical extensions and serve slidably to support the extensions for vertical sliding movementl with respect to the slideways. By reason of the fact that the cross plates 4l which define the sideways as fo the vertical extensions of the electrode supporting arms constitute a part of the bracket structure I2 and are rigidly connected to the arm 28, the electrode Supporting members. together with the electrodes, swing coniointly with the bracket structure and roof in connection with shift thereof away from and to the shell I0. The electrode supporting members I5 are raised and lowered by way of piston-cylinder devices IIS. These devices con sist of cylinders I I'I and pistons H8 and extend lengthwise of, and are partially disposed in, the vertical extensions IIE. The lower ends of the cylinders II'I rest upon the bottom parts of U- shaped stirups H9. The upper ends of the side parts of such stirups are welded or otherwise xedly secured to the lower portions of the cross plates II'I. The pistons Ilil are slidabiy mounted in the cylinder lill. As shown in Figure 4, the

upper ends of the pistons extend through stuffing boxes I2@ at the upper ends oi the cylinders II`I and abut against the plates lI4 at the upper ends of the vertical extensions H2. The lower ends of the cylinders are provided with ports I2I whereby uid under pressure may be introduced therein or withdrawn therefrom. When uid underpressure is introduced into the lower ends of the cylinders the pistons are forced upwards and cause raising of the electrodes. Withdrawal of fluid from the lower ends of the cylin ders Ill results in downward shift of the pistons and resultant lowering of the electrodes. In connection with operation of the furnace the flow of iiuid under pressure to and .from the lower ends of the cylinders is automatically controlled so as to effect the proper feed of the electrodes with respect to the shell I0.

Operation When it is desired to use the furnace the electrodes I4 are first raised until their lower ends are above the top portion of the refractory lining I8 of the shell Ill. Thereafter the roof II is raised relatively to the bracket structure I2. As heretofore pointed out, raising of the roof is effected by introducing fluid under pressure into the nipple IIII so as to force downwards the piston 92 of the cylinder-piston device 84. Downward. movement of the piston results in turning of the sector shaped sheaves 'I8 in a clockwise direction as viewed in Figures 1 and 5, and resultant raising of the roof. As soon as the roof is raised so that it is clear or free of the top portion of the lining I8 of the shell the cylinderpiston device 59 is operated so as to swing the bracket structure I2 laterally away from the shell I0. As soonvas the bracket structure is swung to its fullest extent away from the shell the roof II exposes the open top of the shell so that the shell may be charged with the metallic material to be reduced to molten form. After charging of the shell the bracket structure I2 is swung back into its normal position wherein the U-sliaped frame 30 and the roof II overlie the shell. Re-

turn swinging of the bracket structure is effected by introducing fluid under pressure into the outer end of the cylinder 60 via the nipple 'I3 and venting the nipple 12. After return of the bracket structure to its normal position the roof II is lowered into sealed relation with the top portion of the refractory lining I8 of the shell. Lowering of the roof is eiected by introducing iiuid under pressure into the lower end `of the cylinder 9| via the nipple |00 and venting the nipple IIII. After lowering of the roof the electrodes I4 are shifted downwards until the lower ends thereof are in proper position with respect to the charge of material in the chamber 2l. As soon as the electrodes are in place current is supplied to them so as to produce the necessary heat to reduce the material to molten form. As soon as the charge of material is melted the shell -I0 with the rooi' in place thereon is tilted so as to effect. discharge of the molten metal via the spout I5. At the conclusion of the pouring op eration the shell is tilted back to its normally upstanding position The herein described electric arc furnace effectively and efliciently fulfills its intended purpose and requires infrequent replacement ofthe refractory lining of the shell by reason of the fact that the roof is suspended for raising and lowering relatively to the bracket structure and hence when in its operative or closed position its weight only is imposed on the lining of the shell. Because of the design, construction and arrangement of the suspension means for the roof butV a small amount of time is required to eect charging of the shell and the operating cycle of the furnace may be carried out with suchgreat rapidity that the furnace is capable ci melting a maximum amount of metallic material.

rEhe invention is not to be understood as restricted to the details sei'l forth since these may be modied within the scope of the appended claims without 'departing from the spirit and scope of the invention.

Having thus described the invention what we A claim as new and desire to secure by Letters Patent is:

i. An electric arc furnace comprising a shell having a discharge spout at the side thereof and mounted so that it may be tilted for discharge purposes,`a bracket structure having a frame part that is horizontally disposed when the shell is vertically positioned, and connected to the shell so that it is movable sidewise back and forth between a position wherein the frame part overlies the shell and a position wherein said frame part is disposed at one side of the shell, a roof for the shell located beneath the frame part of the bracket structure and provided with a hole therethrough, means mounted on the bracket structure and arranged and adapted to raise and lower the roof relatively to said frame part and also connect the roof to said structure so that it is movable sidewise therewith, an electrode extending normally through the hole in the roof, and supporting means for the electrode carried by said bracket structure and independent of the i'lrst mentioned means.

2. An electric arc furnace of the top charge varietyY comprising a tiltable shell, a bracket structure having a frame part that is horizontally disposed when the shell is vertically positioned, and connected pivotally to the shell so as to swingV sidewise back and forth between a normal position wherein the frame part overlies the shell and a second position wherein the frame part is disposed at one side of the shell, a roof for the shell located beneath the frame part of the bracket structure and provided with a hole therethrough, means mounted on the bracket structure and arranged and adapted to raise and lower the roof relatively to said frame part and also to connect the roof to the structure so that it swings therewith, an electrode extending normally through the hole in the roof, and means for supporting the electrode carried by said bracket structure and independent of the i'lrst mentioned means.

3. An electric arc furnace oi the top charge variety comprising a tiltable open top shell, a bracket structure pivotally connected to the shell side wall to swing sidewise to and from the latter and having a frame part arranged so that it overlies and is spaced above the shell when the structure is swung toward the shell, a roof `for the shell located beneath the frame part and provided with a hole therethrough, means mounted on the bracket structure, arranged and adapted to raise and lower the roof relatively to said frame part of the structure and also to connect the roof to the structure so that it swings therewith, and including flexible velements depending from the frame part and having the lower ends thereof anchored to the roof, an electrode extending normally through the hole in the roof, and supporting means for the electrode carried by said bracket structure and independent of the first mentioned means.

It. An electric arc furnace of the top charge" type comprising a tiltable shell, an upstanding shaft positioned outwards of the side wall of the.

shell and having the lower end thereof xedly connected to said side wall, a bracket structure comprising, an upstanding tubular part mountedv rotatably on the upper end of the shaft so that the structure as a whole is capable of swinging laterally to and from the shell, and also coinprising a frame part arranged so that it overlies and is spaced above the shell when the structure is swung towards the shell, a roof for the shell located beneath the frame part of the bracket vstructure and provided with a hole therethrough, means mounted on the bracket structure, arranged and adapted to raise and lower the roof relatively to the structure and also to connect the roof to the structure so that it swings therewith, and including elements depending from the frame part and having the lower ends thereof anchored to the roof, an electrode extending normally through the hole in the roof, and supporting means for the electrode carried by said bracket-structure and independent of the roof raising and lowering means.

5. An electric arc furnace of the top charge variety comprising a tiltable open top shell, a bracket structure pivotally connected to the shell side wall to swing sidewise to and from the latter and having a frame part arranged so that it overlies and is spaced above the shell when the structure is swung toward the shell, a roof for the shell located beneath the frame part of the bracket structure and provided with a hole therethrough, means mounted on the bracket structure, arranged and adapted to raise and lower the roof relatively to said frame part and also to connect the roof to the structure so that it swings therewith, and including elements depending from the trarne part and havingthe lower ends thereof anchored to the roof, an electrode extending normally through the hole in the roof, supporting means for the electrode carried by said bracket structure and independent' of the rst mentioned means, and power means 1 between the shell and the bracket structure for swinging the latter to and from the shell.

6. An electric furnace of the top charge type comprising a shell, an upstanding shaft positioned outwards of the side wall of the shell and having the lower end thereof xedly connected to said side wall, a bracket structure comprising an upstanding tubular part mounted rotatably on the upper end of the shaft so that the structure as a whole is capable of swinging laterally to and from the shell, and also comprising a frame part arranged so that it overlies and is spaced above the shell when the structure is swung towards the shell, a roof for the shell, means mounted on the bracket structure, arranged and adapted to raise and lower the roof relatively tn the structure and also to connect asaaeea 9 arranged so that it overlles and is spaced above the shell when the structure is swung towards the shell, a roof for the shell, means mounted on the bracket structure, arranged and adapted to raise and lower the roof relatively to the structure and also connect the roof to the structure so that it swings therewith, and including flexible 4 elements depending from the frame part and having the lower ends thereof anchored to the roof, upstanding electrodes extending slidably through holesl in the roof, and upstanding electrode supporting members` embodying cantilever type arms with clamps at their outer ends for the electrodes and vertical extensions connected to, and depending from, the inner ends of the arms and mounted slidably in said slideways.

13. An electric arc furnace of the top charge variety comprising a tiltable open top shell, a bracket structure connected pivotally to the shell side wall so as to swing sidewise to and from the shell and having a normally horizontal frame part arranged so that it overlies and is spaced above the shell when the structure is swung towards the shell, a roof for the shell located beneath the frame part of the bracket structure and having a hole therethrough, power actuated means mounted wholly on the bracket structure and arranged and adapted to raise and lower the roof relatively to said frame part, and also to connect the roof to the structure so that it swings therewith, an electrode extending normally through the hole in the roof and into the shell, and means for supporting the electrode carried by said bracket structure and independent of said power actuated means.

la. .An electric furnace of the top charge variety comprising a shell, a bracket structure pivotally connected to the shell side wall to swing laterally to and from the latter and having a frame part arranged so that it overlies, and is spaced above, the shell when the structure is swung towards the shell, and provided with sheaves, a roof for the shell disposed beneath the frame part of the bracket structure, ilexible elements trained around the sheaves and having certain ends thereof anchored to the roof, and means on the bracket structure for winding up the flexible elements to effect raising of 'the roof relatively to the frame part and also paying out the flexible elements in order to eiect lowering of the roof relatively to the frame part.

l5. An electric furnace of the top charge variety comprising a tiltable shell, a bracket structure pivota'lly connected to the shell side wall to swing laterally to and from the latter and having a frame part arranged so that it overlies, and is spaced above, the shell when the structure is swung towards the shell and provided with sheaves, a roof for the shell disposed beneath the frame part of the bracket structure, ilexible elements trained around the sheaves and having certain ends thereof anchored to the roof, and power actuated means on the bracket structure for Winding up the flexible elements to effect raising of the roof relatively to the frame and also paying out the exible elements in order to eect lowering of the roof relatively tothe frame part.

16. An electric furnace of the top charge variety comprising a shell, a bracket structure pivotally connected to the shell side wall to swing laterally to and from the latter and having a frame part arranged so that it overlies, and is spaced above, the shell when the structure is swung towards the shell and provided with sheaves, a roof for the shell disposed beneath the frame part of the bracket structure, flexible elements trained around the sheaves and having certain ends thereof anchored to the roof, and means including a cylinder-piston device on the bracket structure for winding up the flexible elements to eifect raising of the roof relatively to the frame part and for paying out said elements in order `to effect Ylowering of the roof structure with respect to said frame part.

17. An electric furnace of the top charge variety comprising a shell, a bracket structure connected pivotally to the shell to swing laterally to and from the latter and having a frame part arranged so that it overlies,` and is spaced above, the shell when thestructure is swung toward the shell and provided with a plurality of sheaves, a

- roof for the shell disposed under the frame part of the bracket structure, a plurality of ilexible elements associated respectively with, and depending from, the sheaves and having the lower ends thereof anchored to the roof and their upper ends extending around and adjustably connected to said sheaves, and power means mounted on the bracket structure and adapted to rotate the sheaves so as to wind up the iiexible elements and eiect raising of the roof relatively to the frame part and also to rotate the sheaves reversely so as to pay out the ilexible elements and effect lowering of the roof with respect to said frame part of the bracket structure.

18. An electric are furnace of the top charge type comprising a tiltable open top shell, an upstanding shaft positioned outwards of the side wall of the shell and having the lower end thereof lxedly connected to said side wall, a bracket structure comprising an upstanding tubular part mounted rotatably on the upper end of the shaft so that the structure as a whole is capable of swinging laterally to and from `the shell, and also comprising a frame part arranged so that it overlies and is spaced above the shell when the structure is swung towards the shell, a roof for the shell located beneath the frame part of the bracket structure and provided with a hole therethrough, means mounted on the bracket structure, arranged and adapted to raise and lower the roof relatively to the structure and also to connect the roof to the structure so that it swings therewith, and including elements depending from the frame part and having the lower ends thereof removably connected to the roof, an electrode extending normally through the hole in the roof and into the shell, and supporting means for the electrode carried by said bracket structure and independent of the roof raising and lowering means. Y

19. An electric arc furnace of the top charge type comprising a tiltableshell, an upstanding shaft positioned outwards of the side wall of the shell and having the lower end thereof rlxedly connected to said side wall, a bracket structure comprising an upstanding tubular part mounted on the upper end of the shaft so that it is rotatable relatively thereto without axial displacement and coacting with said upper end of the shaft to support the structure so that it is capable of swinging laterally to and from the shell, and also comprising a frame part arranged so that it overlies and is spaced above the shell when the structure is swung toward the shell, a roof for the shell located beneath the frame part of the bracket structure and provided with a hole therethrough,

means mounted en the bracket structure, erranged and adapted to mise and mwen the reef relatively to the structure and else connect the roof to said structure se that it swings therewith, and including an element depending mm the fre/me [and having the lewef end ''.he'reef gemev- @my connected to the mmf, en eecbrede extending normally through the hele in the Teef and im@ he shell, and supporting means for the eeetrede carried by seid brame?, structure and a@ independent of the roof raising end lewem'lng means. V

20. An electric fumeee the mp emmge type eemprisng e shell, e breekes siametm'e piv @muy eonmected te *che shell fue swing leteey e end imm the latter, e frame pam er :ranged so that it @verlies mais spaced above' 15:11a 

